A new study led by Stanford Medicine has found a surprising link between the shingles vaccine and a lower risk of dementia.
The research, published in Nature, shows that older adults in Wales who received the shingles vaccine were about 20% less likely to be diagnosed with dementia over the next seven years compared to those who didn’t get the shot.
A second study published in Cell also found that the vaccine might help slow the disease in people who already have dementia.
Shingles is caused by the varicella-zoster virus, the same virus that causes chickenpox. After someone has chickenpox, the virus stays in their body for life.
Later in life, the virus can become active again and cause shingles. Shingles leads to a painful rash and is more common in older adults or people with weak immune systems.
Dementia affects over 55 million people worldwide. Scientists have mostly focused on changes in the brain caused by abnormal proteins, like the plaques and tangles found in Alzheimer’s disease.
But many treatments aimed at these brain changes haven’t worked well. So, some researchers are now looking at other possible causes of dementia, such as infections from viruses that may damage the brain over time.
Earlier studies hinted that people who got the shingles vaccine had a lower chance of developing dementia. However, these studies had a problem: people who choose to get vaccines often have healthier lifestyles, and those differences could affect the results.
To get around this problem, Stanford researchers found a unique situation in Wales that allowed for a better comparison.
In 2013, Wales launched a shingles vaccine program that only included people who were 79 years old on September 1 of that year. People who were even one day older were not eligible. This rule created a natural experiment.
By comparing people who had birthdays just before and just after the cutoff date, researchers could study groups of people who were nearly identical in age, but only one group had access to the vaccine.
The researchers analyzed health records from over 280,000 older adults who did not have dementia when the program began. They followed these individuals for up to nine years. They found that the group eligible for the vaccine had fewer cases of dementia and even fewer deaths caused by dementia.
Those who got the vaccine also had a lower chance of developing mild cognitive problems and seemed to experience slower progression of dementia if they already had it.
One surprising finding was that the vaccine’s benefits appeared to be stronger in women than in men. This could be due to differences in how immune systems respond or how dementia develops in different sexes.
No one knows for sure how the vaccine may protect against dementia. It might boost the immune system, reduce how often the virus reactivates, or work in some other way. It’s also unclear if newer versions of the vaccine will have the same or even better effects.
These results have been supported by similar findings in other countries, including England, Canada, and Australia. Researchers now hope to launch a randomized controlled trial—the most reliable kind of scientific study—to test the vaccine’s impact on dementia more directly.
If the results hold up, we may already have a simple, safe, and widely available way to help reduce the risk of dementia. A one-time vaccine could make a big difference for millions of people around the world.
If you care about brain health, please read studies about how the Mediterranean diet could protect your brain health, and Omega-3 fats and carotenoid supplements could improve memory.
For more information about brain health, please see recent studies about antioxidants that could help reduce dementia risk, and higher magnesium intake could help benefit brain health.
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